ERROR CODE

RESOLUTION

Locate the Workflow with the invalid user information and then manually re-publish it.

Run a SQL server profile trace - there should be an indication of a location where the problem occurs, for example: _catalogs/wfpub/Approval - SharePoint 2010',@LeafName1=N'ReviewApproval_1033.xoml.wfconfig.xml

Use SharePoint Designer to open the workflow file that is implied to exist by the .xoml.wfconfig.xml file extension. Browse to (in this example) _catalogs/wfpub.

Find the workflow files that are present and attributed to a deleted user and while logged in with a current, valid user, check them out then chec them in to update the "modified by" property.

You should now be able to browse to the pages that were previously producing errors.

ADDITIONAL INFORMATION

This is caused by having a user deleted from the site that was referred to in a published Workflow, most likely as the publisher.